Gadolinium vanadate nanocrystals as carriers of -emitters (225Ac, 227Th) and contrast agents

Gadolinium vanadate (GdVO4) core and core+2 shell nanocrystals (NCs) were evaluated for in vitro retention of Ac-225, Th-227, and their first decay daughters, Fr-221 and Ra-223, respectively. GdVO4 NCs with a tetragonal crystal system (zircon-type) and spherical morphology were obtained by precipitation of GdCl3 and Na3VO4 using sodium citrate as a complexing agent. The growth of two nonradioactive GdVO4 shells on both Gd(Ac-225)VO4 and Gd(Th-227)VO4 core NCs was demonstrated by an increase of 0.7nm and 2nm in the crystallite size, respectively. The maximum leakage of Ac-225 was 15% and 2.4% from core and core+2 shells, whereas the leakage of Th-227 was 3% and 1.5%, respectively. The presence of two nonradioactive GdVO4 shells increased the retention of Fr-221 and Ra-223 by 20% and 15% with respect to core NCs. Furthermore, a longitudinal proton relaxivity, r(1)=0.9289s(-1)mM(-1), confirmed their potential application as contrast agents for magnetic resonance imaging. In summary, GdVO4 NCs show promising capabilities as radionuclide carriers with partial retention of decay daughters and as contrast agents for theranostic applications.